Pit prop unit sensing devices

ABSTRACT

This invention relates to a pit prop unit having a device which acts to sense obstructions located in the vicinity of the working face and in the path of the self-advancing mine-roof support unit as it moves forward, this device having a thrust-piston mechanism actuated by pressurized fluid and attached to a cap piece on the forward side of the unit, the thrust-piston mechanism being extended by a laterally flexible sensor which acts to feel an obstruction and finds abutment against it to counteract the thrust of the thrust-piston mechanism.

limit 1 Inventors App]. No.

Filed Patented Assignee Priority llllmns lkieschel Miltcnberg;

Bode-Werner haw, Essen, both of, Germany Sept. 10, 1969 Aug. 311, 1971 lller gwerlrsverlbandl Gmbi-ll lEssen-Kray, Germany Sept. 20, 1960 Germany WT P111011 UNIT SENSING DEVICES 2 claims, 3 Drawing lFigs.

US. (11 61/45 1) lint. Q1 lEZld 23/06 ll ielrl of Search 61/45;

[56] References Cited UNITED STATES PATENTS 3,392,531 7/1968 Ratz .1 61/45 3,392,532 7/1968 Jacobi 61/45 3,397,543 8/1968 Spies et a1 61/45 Primary Examiner-Dennis L. Taylor Attorney-Mlalc0lm W. Fraser ABSTRACT: This invention relates to a pit prop unit having a device which acts to sense obstructions located in the vicinity of the working face and in the path of the self-advancing mineroof support unit as it moves forward, this device having a thrust-piston mechanism actuated by pressurized fluid and attached to a cap piece on the forward side of the unit, the thrust-piston mechanism being extended by a laterally flexible sensor which acts to feel an obstruction and finds abutment against it to counteract the thrust of the thrust-piston mechanism.

ATENTED M1831 I973 3.601897 INVENTORS M) m. MPM

lPllT FRO]? UNIT SENSING DEVll ClES BACKGROUND OF THE INVENTION Such devices render possible the automatic step-by-step advance of a hydraulic mine-roof support unit in that they ascertain, in accordance with the length of the sensor extended, whether the distance required for the advance by one step of the roof-support unit, from the tip of the cap piece to the working face or to an obstruction, is or is not available ahead of the cap piece. It is therefore on the one hand essential to protect the sensors from damage; on the other hand, however, a sensor must also be able to determine by mechanical means any irregularities in the position around the working face, for instance any fissures or faults in the gallery roof that run upwards or downwards.

PRIOR ART It is an already known technique to accommodate sensors with their thrust-piston mechanisms in a protective manner in special housings beneath the cap pieces, and to control the admission of fluid to these thrust-piston mechanisms by means of the hydraulic mechanisms controlling advance of the units. By these means the sensors move outwards from or retract into the protective housings at certain intervals of time. The probability of damage to the sensors is decreased in this way. The control system necessary for this operation is, however, comparatively expensive in material, and special housings are undesirable because of the restriction of gallery space.

The thrust-piston mechanism is generally fastened beneath the cap piece so as to pivot about a generally horizontal axis. The axis of the cylinder is normally inclined with respect to the plane of the upper operative surface of the cap piece, with the consequence that, upon the extension of the rod constituting the sensor, whose front end is generally provided with a sensing head, the latter travels obliquely upwards. If the roof of the gallery forms a single plane with the upper surface of the cap piece, then the sensing head will slide along the roof until it reaches an obstruction, for example the working face. Within certain limits, the pivotal suspension of the thrustpiston mechanism can facilitate deflections of the sensing head due to fissures or faults in the roof.

In this arrangement, however, the considerable height of the structure proves a drawback; as trials in mines have shown, even with only moderate thicknesses of seam and with properly loaded conveyor equipment the danger exists that the material being transported will reach as high as the lower edge of the cap piece on the side towards the working face, and will damage the sensors or the thrust-piston mechanisms appertaining thereto.

Finally, the experiment has already been undertaken whereby the thrust-piston mechanism for actuating the sensor is installed inside the cap piece. Hitherto this has only been possible if the thrust-piston mechanism has not been pivotable, but is fixedly mounted. Then, however, an unsatisfactory sensing operation is the result, especially with respect to irregularities in the course of the seam.

OBJECT OF THE INVENTION The invention has for its object to provide a device for sensing, the thrust-piston mechanism of which is built into the cap piece but the sensor of which is able to follow the course of the adjacent rock, and more especially of the roof, in the immediate vicinity of the tip of the cap piece even when quite large breaks in the line of the roof are present.

BRIEF SUMMARY OF THE INVENTION According to the invention, the thrust-piston mechanism is extended in length by a sensing rod which is led out from the cap piece at an acute angle to the plane of the operative cap piece surface and is formed to be flexible transversely to its longitudinal axis.

The device has the advantage that the sensor is able to follow even quite large irregularities in the rock or at the working face and by this means avoids transmitting erroneous bits of information when the roof-support unit merely requires to advance beneath a break in the line of the roof, or has to follow a break running upwards. Immediately, however, a larger obstruction, such as is constituted, for instance, by the working face, comes in the way of the sensor, the sensing rod presses against this obstruction and is no longer extended by the thrust-piston mechanism. In this way the force exerted by the thrust-piston mechanism is taken up against the obstruction, and an indication is given that the way for the step-by-step advance of the r0of-support structure is not yet free.

FURTHER FEATURES OF THE INVENTION These conditions are preferably fulfilled by a sensing rod consisting of a tension spring which is wound with a degree of prestressing and which is able to accommodate comparatively large forces in the axial direction, but is also easy to deflect transversely.

The tension spring is preferably wound about a straight axis; then the tension spring can be angled with the aid of fixed guide means which may be built into the cap piece, so that the spring at the point of emergence from the guide means extends at an acute angle to the cap piece surface.

Such guide means, along with a pivoting facility for the thrust-piston mechanism at its end remote from the guide means, offers a completely adequate: but very simple realignment means for the sensing device in the cap piece of the roof support unit.

DESCRIPTION OF EMBODIMENT Further features of the invention are explained in greater detail hereinafter with reference to the example shown in the accompanying drawings, in which:

FIG. 1 shows, viewed from the side and in section through the front end of a cap piece located on the forward side of a mine-roof support unit adapted to advance step-by-step, a sensor and its thrust-piston mechanism in. a retracted position;

FIG. 2 shows the sensor and its thrust-piston mechanism correspondingly to FIG. 1 but in an extended position; and

FIG. 3 shows, in a corresponding manner to FIGS. 1 and 2, the situation occurring due to a break in the line of the roof and at the time when the sensor has reached the working face.

A cap piece 1 is located on the forward side of a self-advancing pit prop unit, this cap piece consisting of hollow metal section which serves to support the roof 2 of the mine gallery. In the cap piece is installed a hydraulic thrust-piston mechanism 3, which consists of a cylinder 4 which is pivotally I mounted at 6 adjacent its closed end 5 and from which emerges a piston rod 7 to which, with the aid of a coupling 8, is fastened a sensing rod 9, which may be considered to extend the reach of the thrust-piston mechanism 3.

The sensing rod is formed of a tension spring which is wound with a degree of prestressing, although this is not shown in the drawing. If the said tension spring, which is wound about a straight axis, is subjected to pressure in the direction of its axis of winding, it is able to absorb with little compression comparatively large compressive forces. Consequently, under these conditions, the sensing rod 9, at the free end of which a sensing head 10' is attached, is able to counteract the full force of the thrust-piston mechanism 3 if the sensing head 10 meets head-on with an obstruction.

In the region of the front tip of the cap piece a guide means ll 1 is located which covers a fraction of the length of the rod 9. The guide means has a curved channel 12 which causes the rod 9, as shown in FIG. 2, so to emerge from the tip ll of the cap piece that the longitudinal axis 13 of the rod 9 in that portion of the rod emerging from the guide means ll makes an acute angle a with the plane 14 of the roof-supporting cap piece surface.

This has the consequence that, when the piston rod 7 is pushed out of the cylinder 4, the rod 9 is directed obliquely against the roof 2 and strikes the roof a short distance in front of the tip 1 la of the cap piece.

As a result of the innate flexibility of the tension spring in directions transverse to its longitudinal axis, the rod is deflected, so that the head 10 of the sensor follows the roof line.

In the event that the thrust-piston mechanism 3 attains itsfull extension because the head 10 has not met with any obstruction, then by this means it will have been ascertained that no obstruction, such as might endanger the forward move ment of the pit-prop unit advancing step-by-step, is present in the path of the unit.

In the case of FIG. 3, however, it is assumed that the working face has not yet been cut away, as a result of being worked, so that complete extension of the thrust-piston mechanism is not possible. Further, it is assumed that in the line of the roof 2 there is a break 2a which is overcome by the cap piece 1 taking up an oblique position.

Under these circumstances the rod 9 extends outwards, and again follows the course of the roof in the area of the break 2a If the head 10 now meets against the face 15, not yet sufficiently cut away, the rod 9 is subject to loading in the axial direction, in which it exerts a force opposed to the thrustpiston mechanism, the said force preventing further extension of the piston rod 7 from the cylinder 4. By this means information is supplied that an obstruction is located in the path of advance of the pibprop unit.

We claim:

1. In a self-advancing pit prop unit having a roof-engaging hollow cap piece supporting the roof of a mine and provided with an opening in its outer end, a device for sensing obstructions in the path of advance of the unit comprising:

a fluid pressure operated piston and cylinder assembly;

means supporting said assembly within the cap piece;

a sensing rod forming an extension of the piston rod arranged to extend through the opening in the cap piece, said rod being resiliently flexible transversely with respect to its longitudinal axis; and

a guide in the cap piece having a channel through which said sensing rod passes, said channel being curved to cause bending of said sensing rod at an acute angle to the plane of the roof-engaging surface of the cap piece, thereby to ride along the mine roof above the cap piece to determine any obstruction to the advance of the pit prop unit.

2. A sensing device according to claim 1, wherein the sensing rod consists of a tension spring wound with a degree of prestressing about a substantially straight axis to counteract the force of the piston rod when the sensing rod encounters an obstruction. 

1. In a self-advancing pit prop unit having a roof-engaging hollow cap piece supporting the roof of a mine and provided with an opening in its outer end, a device for sensing obstructions in the path of advance of the unit comprising: a fluid pressure operated piston and cylinder assembly; means supporting said assembly within the cap piece; a sensing rod forming an extension of the piston rod arranged to extend through the opening in the cap piece, said rod being resiliently flexible transversely with respect to its longitudinal axis; and a guide in the cap piece having a channel through which said sensing rod passes, said channel being curved to cause bending of said sensing rod at an acute angle to the plane of the roofengaging surface of the cap piece, thereby to ride along the mine roof above the cap piece to determine any obstruction to the advance of the pit prop unit.
 2. A sensing device according to claim 1, wherein the sensing rod consists of a tension spring wound with a degree of prestressing about a substantially straight axis to counteract the force of the piston rod when the sensing rod encounters an obstruction. 